This invention relates to human T-lymphocytes ("T-cells").
The T11 sheep erythrocyte binding glycoprotein [relative molecular mass (M.sub.r) 50,000-55,000] is expressed throughout human T-lymphocyte ontogeny and appears to play an important physiological role in T-cell activation. The treatment of T cells with certain monoclonal anti-T11 antibodies results in antigen independent polyclonal T-cell activation as assessed by proliferation and lymphokine secretion. In addition, the majority of thymocytes that have not yet acquired the T3-Ti antigen/major histocompatibility complex (MHC) receptor can be activated to express interleukin-2 (IL-2) receptors through this T11 structure.
Three distinct epitopes on the 50K T11 molecule have been identified. While the T11.sub.1, and T11.sub.2 epitopes are expressed on resting as well as activated T cells, anti-T11.sub.3 antibodies recognize a spatially distinct epitope that is preferentially expressed on mitogen- or antigen-activated T lymphocytes and thymocytes. The T11.sub.3 epitope appears to represent a conformational change since it can be induced on resting T cells within 30 min at 4.degree. C. by treatment with anti-T11.sub.2. These studies have also shown that the combination of anti-T11.sub.2 and anti-T11.sub.3 (and to a lesser extent certain anti-T11.sub.1 and anti-T11.sub.3 antibodies) can induce IL-1-independent polyclonal T-cell activation as measured by proliferation and lymphokine secretion.